Thermostat



H. H. FOGWELLAND J. M. MORRIS. THERMOSTAT.

APPLICATION FILED Nov. Is, 1911.

erica.

HARRISON' E. FOGWELL AND JOHN' M. MORRIS, OF LOS ANGELES, CALIFORNIA.

THERMOSTAT.

Specification of Letters Patent.

Patented Nov. 29, 1921.

To all whom t may concer/n:

Be it known that we, HARRISON H. FOG- WELL and .JOHN M. MORRIS, both citizens of the United States, residing at Los Angeles in the county of Los Angeles and State oi:2 California, have invented a new and useful Thermostat, of which the following is a specification.

Our invention relates to the temperature control of electric currents, andmore particularly to a novel form of thermostat by means of which an electric circuit is opened or closed as the temperature of the thermostatic element is varied.

The principal object of the invention is to provide a novel form of thermostat which is particularly adapted for use in applying electric heaters to conventional designs of hot water tanks.

rlhe invention consists in the construction and novel combination and arrangement of parts hereinafter described as illustrated in the accompanying drawings, and pointed out in the claims hereunto appended.

In these drawings,

Figure 1 is a sectional elevation showing our invention applied to a standard hot water tank.

Fig. 2 is a central section on an enlarged 'scale through the .thermostatic device.

Fig. 3 is a section on a bent plane represented by the line 3-3 of Fig. 2.

. Fig. 4 is a view on an enlarged scale of the moving contact.

The thermostat consists of a thermostatic element 11 which is inclosed in a case 12 having a cover 13 held in place by screws and nuts 14. The thermostatic element 11 consists of two strips of dissimilar materials which have different co-eilicients of'expansion. The thermostatic element 11 is secured inside the case 12 near the upper end thereof by means of bolts 15, the lower end of the thermostatic element 11 carrying a small pin 16 .to which a thermostatic rod 17 is pivoted. The thermostatic rod 17 passes through a tube 18 which is rigidly secured at 19 in the cover 13, the tube 18 being alsov threaded or otherwise secured in a switch case 20. This switch case 20 is formed of cast iron and is provided with a cover 21 secured in place by screws 22. The thermostatic rod 17 passes through an insulating .block 3() being secured therein by means of thumb nuts 31 and 32. The block 30 is provided with a pin 33 to which are pivoted a pair of links 34, one on either side of the block 30, these links being in turn pivoted on a pin 35 carried in the case 20. Secured on the block 30 and carrying the pin 33-is a keeper 40 formed of sheet iron, this keeper being so placed that it makes contact with the poles 41 and 42 on a permanent magnet 43. The magnet 43 is held inside the case 20 by a cast iron bracket 44 and a screw 45. A magnet shunt 46 is secured between the pole pieces 41 and42 for reasons which will hereinafter be explained.

Carried on the insulating block 30 is ya metal member 50 having a hole 51 therein. Fitting loosely in the hole 51 is a screw having a body- 52 and a head 53, the head 53 being lat to provide a Contact surface 54. Secured between two nuts 55 at the other end of the screw 52 is a connector 56 to which a flexible lead 57 is soldered. A

washer 58 and compression spring 59 tend to hold the screw 52 at right angles to the plate 50 at all times.

Secured on a bracket 60, carried on an insulating slab 61, is a stationary flexible lcontact 62, this contact consisting of a flat strip 63 with a contact 64 carried at its extreme outer end. A lead 65 is connected by means of a screw 66 on one end of the strip 62, and a lead 67 is connected to a connector 68v carried on the slab 61, the lead 57 being also secured to the connector 68. The leads 65 and 67 pass through an insulating bushin 69 fixed in the side ofkthe case 20.

ile the above describedthermostat has various uses, it is ,particularly useful in the installation of 4electrical heating .devices to existing forms of hot Water tanks. Such a tank is shown at 70 in Fig. 1 and is ordinarily provided with a cold water inlet ipe 71 and a hot Water outlet pipe 72. uch tanks are ordinarily provided with a bottom 73 and this bottom is ordinarily provided with a central outlet 74 through which an electric heating element 75 may be conveniently inserted. The case 12 of the thermostat is then secured to the side of the tank r-terior of the heater completely covering' the thermostat case 12, the tube-18 being of suflicient length to pass through such a lagging placing the case 20 entirely outside the lag- '70 preferably by means of metal straps 76 wire .82 with any convenient source of elecging. The wire 65 is then attached to one terminal 8U of the electric heater 75, the other terminal 81 being connected with a tric, ,purrent, the wire 67 being connected to the same source.

In the application Iof electricity to the heating of water for domestic purposes, itis found that the demand for hot water occurs durin the early evening hours, at which time the peak load ofthe centrall stations is ordinarily at its maximum. For the purpose of'so regulating the heating of water in the tank 70 as to make it an attractive commercial proposition to the central stations furnishing the current so that they can make a low flat rate for such heating, it is necessary to so arrange the heater that the heating element 75 will not be in circuit ordinarily during the evening peak load period of the central stations. For this purpose we secure the thermostatic element 11 to the exterior of the tank 70 at a distance approximately one-third of the way up from the bottom. When-so secured, the method of operation is as follows The tank 70 being filled with cold water through the pipe 71, the thermostatic ele- `men`t 1s in the position shown in thedrawings with the armature in contact with the poles 41 and y42, and with the contact surfaces 54 and 64 in intimate electrical'contact. The current then iows from the wire -67 to the wire 65 through the heater 75 thereby raisin the temperature of this heater and heatmg the water in the tank 7 0.

, This heating continues by convection at a .thereby tending to .force the rod 17 in that direction and exerting considerable pressure on the insulating block 30. f

The pole pieces 41. and 42 of the permanent magnet 43 exert an attraction on the armature 40 which resists the thrust of the rod 17. The amount ofl this attraction may be .varied by varying the size ofthe magnet shunt 46. This magnet shunt permits a con siderable proportion ofthe magnetic iux to ,pass so that theLtotal force of the magnet l43 is not exerted on the varmature 40. This allows an. adjustment vof the magnet pull on the armature 40an also tendsto greatlyreduce Athe `-loss of `magnetism of the permanent magneti-43 with the passage of time.

4VVvhenever*the thermostatc `element. 11y has been sufiiciently heated to develop. sulcient point below the position in which the thermostatic element is placed, in other words, the tank is practically full of hot water at the time the heating element 75 is shut off. By covering the tank 7 O with the lagging 78 the heat losses therefrom are rendered very small so that the tank can stand for a considerable period without serious loss of heat providingno water is drawn therefrom.

As some demand for water occurs during the preparation of the evening meal, or more often immediately thereafter for the puri pose, of washing dishes, etc., it is found in practice that the heater operates during the day to bring the water up to the desired temperature, and that during the early evening some of this hot water is drawn off. As the hot water is drawn olf through the pipe 72 it is replaced with cold water introduced through the pipe 71. heater 75 shut olf so that there is no convection circulation inside the tank .70, the'cold water tendsto stratify, remaining in the bottom lof the tank gradually displacing the hot water which is drawn ott through the top of the tank. This continues until the level of the cold water is carried considerably above the thermostatic element 11, as it takessome time for the cold water to extract suicient heat through the walls of the tank 7 O and the case 12 to effect the thermostatic element. As a matter of fact, probably one-third of the hot water is drawn off before the thermostat acts to pull the block 30'in a direction opposite tothe arrow A. As soon as this occurs the block moves 'over slowly to thel left under the vvgradual movement induced by the thermostatic element 11 until the armature 40 com-j mences to come into the magnetic ield of the pole pieces 41 and 42 to a suiicient extent for them to exert an appreciable pull -thereon.\ Whenever this occurs the magnet 43 acts to assist they thermostatic Velement 1l, making4 an instantaneous'contact. The contact surfaces 54-and 64 .are so adjusted that they touch each other'befo're'the. arma-- ture 40 fully seats on the pole pieces 41 and 42 with. the resultv that the flexible strip 62 -isbe'nt slightly thereby putting a denite and constant pressure between the contact surfaces 54 and 64. Y

I Theconstruction of the screw 52 and its With the method of attachment in the plate 50 allows considerable iexibility between the plate 50 and the screw 52 so that a square contact ispossible at all times. Whenever the contact surfaces 54 and 64 touch, current is thrown into the heater 75 and the heating peated.

-By locking the thermostatic element in.

the position shown and described above, it is necessary to draw off suHicient hot water to raise the cold water level above the point of attachment to the thermostat, and it is thus possible to make considerable demands on the supply of hot water without causing the thermostat to operate and energize the heating element. By so doing the heater does not ordinarily operate during the peak load of the central station. Whenever the thermostat does operate, however, the convection currents set up by theheating element serve to mix the cold water from the bottom of the tank with the hotter water above so that the tank is uniformly heated without any noticeable stratification. This is made possible by the location of the heating element in the bottom of the tank as shown.

What we claim is l. A thermostat for use with a hot water tank comprising a narrow, long and thin case adapted to be clamped in good thermal contact with the outside of said tank; a thermostatic element secured to said case near the upper end thereof and to the side adjacent to the water tank when so clamped; a tube secured in the opposite side of said case; a second case secured to the outer side of said tube; electrical circuit closing mechanism inside said second case; and means by which said element actuates said mechanism throu hsaid tube. f

2. thermostat for use with a hot water tank comprising a thermostat case adapted of the water in the tank 70 is re-V to be clamped in good thermal contact with the outside of said tank at a point intermediate of the height thereof; a thermostatic element in said case; a tube secured in said case; a switch case secured to said tube; a switch in said switch case; and means by which said thermostatic element operates said switch through said tube.

3. A thermostat for use with a hot water tank Icomprising a thermostat case adapted to be clamped in good thermal contact with the outside of said tank at a point intermediate of the height thereof; a thermostatic element in said case; a switch case secured to said thermostat case; a switch in said switch case; and means by which said thermostatic element operates said switch.

4. A thermostat for use with a hot water tank comprising a thermostat case adapted to be clamped in good thermal contact with the outside of said tank' at a point intermediate of the height thereof; a thermostatic element secured to the side of said thermostat case which isy clamped next to said hot water tank; a tube secured in said case; a switch case secured to said tube; a switch in said switch case; and means by which said thermostatic element operates said .switch through said tube.

5. A thermostat for use with a hot water tank comprising a thermostat case adapted to be clamped in good thermal contact with the outside of said tank at a point intermediate of the height thereof; a thermostatic element in said case; a switch case; a switch in said switch case; and means by which said thermostatic element operates said switch.

In testimony whereof, we have hereunto set our hands at Los Angeles, California, this 9th day of November, 1917.

HARRISON H. FOGWELL. JOHN M. MORRIS. 

